Russian opposition leader Alexei Navalny leaves the European court of Human Rights after a hearing regarding his case against Russia at the court in Strasbourg, France, January 24, 2018. REUTERS/Vincent Kessler

MOSCOW (Reuters) - Investigators in Russia summoned opposition leader Alexei Navalny for questioning on Monday, saying they were looking into allegations he had assaulted policemen at an anti-Kremlin protest last month.

Around 1,500 people in Moscow and hundreds more in cities across Russia took to the streets on Jan. 28 in a protest organized by Navalny to support a boycott of presidential elections in March.

Incumbent Vladimir Putin is widely expected to be re-elected, but Navalny says he has been unfairly barred from running over what he says is a trumped-up suspended prison sentence.

Police bundled Navalny off the street in Moscow at the protest and detained him for several hours before releasing him without charge but with talk of a future court appearance.

Navalny said on social media on Monday investigators had delivered two summonses to him, demanding he come in for questioning. He denies assaulting police officers and posted a link to a video of his detention which showed him trying to stay on his feet as several policemen dragged him to a nearby bus.